1. Field of the Invention
The present invention relates generally to a method of controlling particle beams in a multi-particle beam column and, more particularly, to a multi-particle beam column that is provided with an electrode layer having eccentric apertures, thereby being able to easily control particle beams.
2. Description of the Related Art
Particle beam columns include a particle source (emission source) and electron lenses configured to be operated by an electrostatic field or a magnetic field, and generate, focus, and scan a particle beam, such as an electron beam or an ion beam. Representative particle beam columns are electronic columns using an electron beam, and ion beam columns using an ion beam. Such particle beam columns are used in electron microscopes, semiconductor lithography, and various inspection apparatuses, such as apparatuses for inspecting the via/contact holes of semiconductor devices, apparatuses for inspecting and analyzing the surfaces of samples, or apparatuses for inspecting the wiring of the Thin Film Transistors (TFTs) of display devices such as a TFT-Liquid Crystal Display (LCD) and an Organic Light Emitting Diode (OLED) display, which use an electron beam.
The electron beam column is a representative example of a particle beam column. A microcolumn, which is an example of an electronic column for generating, focusing and scanning an electron beam, is fabricated based on an electron emission source configured to emit electrons and minute electron optical parts configured such that the diameters of apertures through which electrons pass are equal to or smaller than sub-500 micrometers, and was first introduced in the 1980s. A microcolumn enables optical aberration to be minimized by allowing minute parts to be elaborately assembled together, thus forming an improved electron column. A plurality of small structures is arranged, and can be then used in a multi-type electron column structure having a parallel or series structure. For this purpose, a lens is formed of a silicon wafer using a semiconductor manufacturing process. The aperture of the lens is fabricated in the form of a membrane using a process of manufacturing a microelectronicmechanical system (MEMS), and the fabricated lens is used as an electrostatic lens.
FIG. 1 is a diagram showing the structure of a microcolumn, and indicates that an electron emission source, a source lens, a deflector, and an Einzel lens are arranged, and scan an electron beam.
In general, a microcolumn, which is a representative very small-sized electron column, includes an electron emission source 110 configured to emit electrons, indicated by arrows in FIG. 1, a source lens 120 formed of three electrode layers in order to emit, accelerate and control the electrons and configured to form an effective electron beam using the emitted electrons, a deflector 150 configured to deflect the electron beam, and a focusing lens (Einzel lens) 140 configured to focus the electron beam on a sample s. In general, the deflector 150 is located between the source lens 120 and the Einzel lens 140. In order to operate the microcolumn in a normal manner, a negative voltage (about −100 V to −2 kV) is applied to the electron emission source 110, and the electrode layers of the source lens 120 are generally grounded. The Einzel lens 140, which is an example of a focusing lens, is used to focus the electron beam by grounding upper and lower electrode layers and applying a negative (−) voltage (in deceleration mode) or applying a positive (+) voltage (in acceleration mode) to a center electrode layer. Based on the same operation distance, the magnitude of the focusing voltage in deceleration mode is lower than that in acceleration mode. Synchronized deflecting voltage is applied to the deflector 150 in order to adjust the path of the electron beam and scan the electron beam onto the surface of the sample s at regular cycles. An electron lens, such as the above-described source lens or focusing lens, includes two or more electrode layers each including an aperture having a circular or predetermined shape at the center thereof so as to allow an electron beam to pass therethrough, and controls the electron beam. It is commonly formed of three electrode layers.
Microcolumns are classified into single-type microcolumns each including a single electron emission source and electron lenses configured to control an electron beam generated by the electron emission source, and multi-type microcolumns each including a plurality of electron emission sources and electron lenses configured to control a plurality of electron beams emitted by the plurality of electron emission sources. The multi-type microcolumns may be classified into wafer-type microcolumns each including a particle beam emission source configured such that a plurality of electron emission source tips is provided in a single layer, such as a semiconductor wafer, and an electron lens configured such that lens layers, in each of which a plurality of apertures is formed, are stacked on each other, combination-type microcolumns each configured to control electron beams, emitted by respective electron emission sources like a single electron column, using a lens layer having a plurality of apertures, and array-type columns each configured such that single electron columns are mounted and used in a single housing. In the case of a combination-type column, electron emission sources are separate, but lenses are used in the same manner as those of the wafer-type column.
The above particle beam column focuses a particle beam generated by a particle emission source and scans the particle beam onto a sample. Depending on the sample, the case of detecting and utilizing ions or electrons using a sample current method is employed. The sample current method that is capable of directly detecting and checking ions or electrons scanned directly onto a sample from the outside because a conductor part of the sample is connected to the outside may be used to inspect the via/contact holes of semiconductor devices, to inspect and analyze the surfaces of samples, and to inspect the wiring of the TFTs of display devices such as an TFT-LCD and an OLED display. However, when the particle beam column is used to conduct the above inspections or to function as a microscope, and is utilized in the form of a multi-particle beam column so as to improve throughput related to processing speed and the like, there arises a problem in that the multi beam column cannot be easily controlled.